Concrete block and method of making same

ABSTRACT

Molds and processes that permit high-speed, mass production of retaining wall blocks having patterned or other processed front faces, as well as retaining wall blocks formed by such processes. The invention permits the front face of the block to be impressed with a pattern or otherwise directly processed, to allow the formation of pre-determined block front faces, while at the same time facilitating high-speed, high-volume production of blocks. A mirror image of the desired pattern can be created on a stripper shoe by selecting a desired three-dimensional surface from a naturally occurring or man made object and digitally scanning the selected three-dimensional pattern to create scanned data. The scanned data can then be used to machine a face of the stripper shoe that is the mirror image of the selected pattern.

RELATED APPLICATION

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 10/038,639, filed on Jan. 4, 2002, which is herein incorporated byreference in its entirety.

FIELD OF THE INVENTION

[0002] The invention relates generally to concrete blocks and themanufacture thereof. More specifically, the invention relates toconcrete blocks suitable for use in landscaping applications, such asretaining walls, and manufacturing processes useful in the production ofsuch blocks.

BACKGROUND OF THE INVENTION

[0003] Modern, high speed, automated concrete block plants and concretepaver plants make use of molds that are open at the top and bottom.These molds are mounted in machines which cyclically station a palletbelow the mold to close the bottom of the mold, deliver dry castconcrete into the mold through the open top of the mold, densify andcompact the concrete by a combination of vibration and pressure, andstrip the mold by a relative vertical movement of the mold and thepallet.

[0004] Due to the nature of such plants and the equipment used toperform this process, it is difficult to impart a natural appearance tothe face of a concrete block, particularly if the block needs to includeother features, such as converging side walls, and an integral locatorand shear flange(s) formed on the top and/or bottom face of the block.U.S. Pat. No. 5,827,015, which is incorporated herein by reference,discloses such a concrete block suitable for use as a retaining wallblock, and the common method for producing such a block in a high speed,automated concrete block plant.

[0005] There is demand for a pre-formed concrete unit, particularly aretaining wall block with converging side walls and/or an integrallocator and shear flange formed on the top and/or bottom face, andhaving a more natural appearing face than is achievable by the splittingprocess described in U.S. Pat. No. 5,827,015, or by the splittingprocess described in U.S. Pat. No. 6,321,740, which is also incorporatedherein by reference. In particular, there is a demand for processes andtooling that will create such blocks with such faces in high-speed,automated fashion on the type of equipment commonly available in aconcrete block or concrete paver plant.

SUMMARY OF THE INVENTION

[0006] The invention relates to molds and processes that permit highspeed, mass production of concrete units, and, in particular, retainingwall blocks. These molds and processes can be used to create relativelysimple decorative front faces on such blocks, similar to the split facesdescribed in U.S. Pat. No. 5,827,015. These molds and processes can alsobe used to create more complex front faces on such blocks, similar tothe split and distressed faces produced by conventional tumbling orhammermill processing, or by the process described in U.S. Pat. No.6,321,740. These molds and processes can also be used to create uniqueblocks that have heretofore not been available: retaining wall blockswith converging side walls and/or integral locator and shear flanges andwith front faces with significantly more complex faces, including faceswith significant detail and relief not heretofore available in dry castconcrete block technology.

[0007] In a preferred embodiment, the resulting blocks have patternedfront faces that simulate natural stone, as well as upper and lowerfaces, a rear face, opposed converging side faces, and a flangeextending below the lower face. Blocks having this construction, whenstacked in multiple courses with other similarly constructed retainingwall blocks, permits construction of serpentine or curved retainingwalls that appear to have been constructed with naturally-occurring,rather than man-made, materials.

[0008] One aspect of this invention is that a mold made in accordancewith the invention is arranged so that the portion of the block thatwill be the front face when the block is laid is facing the open top ofthe mold cavity during the molding process. This orientation permits thefront face of the block to be formed by the action of a patternedpressure plate (“stripper shoe”) in a high-speed, concrete block orpaver plant. The stripper shoe can be provided with a very simplepattern, a moderately complex pattern, or a highly detailed,three-dimensional pattern with significant relief, simulating naturallyoccurring stone. Molding the block in this orientation also makes theblock face readily accessible for other processing to affect theappearance of the face, including the application of specially-selectedaggregate and/or color pigments to the face.

[0009] Another aspect of this invention is that a side wall of the moldhas an undercut portion adjacent the open bottom of the mold cavity.This undercut portion cooperates with the pallet that is positionedunder the mold to form a subcavity of the mold. In a preferredembodiment, this subcavity forms the locator and shear flange on thesurface of the block that will be the bottom of the block as laid.

[0010] Another aspect of this invention is that at least one of the sidewalls of the mold is angled from vertical, to form a side wall of theblock as laid that includes a portion that converges toward the oppositeside wall as it gets closer to the rear face of the block. This angledmold side wall is moveable, so that it moves into a first position topermit the mold to be filled with dry cast concrete and the concrete tobe compacted and densified, and moves into a second position to permitthe densified concrete to be stripped from the mold without interferencefrom this mold side wall. In a preferred embodiment, the opposed moldside wall is similarly moveable, so that at least portions of theopposed side walls of the resulting block converge towards each other asthey approach the rear of the block.

[0011] These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages and objects obtained byits use, reference should be made to the drawings which form a furtherpart hereof, and to the accompanying description, in which there isdescribed a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of a retaining wall block accordingto the present invention, with the block being oriented in the positionin which it is formed in the mold.

[0013]FIG. 2 is a bottom plan view of the retaining wall block of FIG.1.

[0014]FIG. 3 is a side elevation view of the retaining wall block ofFIG. 1.

[0015]FIG. 3A is a detailed view of the portion of the retaining wallblock contained within the dashed circle in FIG. 3.

[0016]FIG. 4 is a front view of a portion of a retaining wallconstructed from a plurality of blocks according to the presentinvention.

[0017]FIG. 5 is a flow chart illustrating the process of forming theblock of the present invention.

[0018]FIG. 6 is a perspective view of a mold assembly having a pluralityof mold cavities for forming a plurality of retaining wall blocks of thepresent invention utilizing the process of the present invention.

[0019]FIG. 7 is a top plan view of the mold assembly of FIG. 6.

[0020]FIG. 8 is an end view of the mold assembly illustrating one moldcavity with opposed, converging, pivoted side walls.

[0021]FIG. 9 is a schematic representation of the side walls that formthe upper and lower block faces, the stripper shoe, and the pallet ofthe mold assembly.

[0022]FIGS. 10A, 10B, 10C, 10D, 10E and 10F are digital renditions ofrepresentative patterns on the faces of stripper shoes according to thepresent invention.

[0023]FIG. 11 is a perspective view of a representative pattern on theface of a stripper shoe.

[0024]FIG. 12 is a flow chart illustrating the process of forming astripper shoe face of the present invention.

[0025]FIG. 13 is a schematic illustration of the temperature control forthe stripper shoe.

[0026]FIGS. 14A, 14B and 14C are photographs of retaining wall blocksaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] Overview

[0028] The present invention provides a process for producing a concreteblock, as well as a block resulting from the process, and a mold andmold components used to implement the process, in which a pre-determinedthree-dimensional pattern is impressed into the face of the block, andthe front face of the block can be otherwise directly processed orworked so that a pre-determined block front face can be produced in astandard dry cast concrete block or paver machine. Direct processing orworking of the front face includes molding, shaping, patterning,impressing, material layering, combinations thereof, and other processesin which the texture, shape, color, appearance, or physical propertiesof the front face can be directly affected. Further, the process can beimplemented using multiple-cavity molds to permit high-speed,high-volume production of the concrete blocks on standard dry castconcrete block or paver equipment. Moreover, use of the inventiveprocess and equipment eliminates the need for a splitting station,and/or a hammermill station, and/or a tumbling station, and theadditional equipment and processing costs associated with suchadditional processing stations.

[0029] The blocks produced by the process of the present invention canhave a configuration that allows construction of walls, includingserpentine or curved retaining walls, by stacking a plurality of blocks,having the same or different pre-determined front faces, in multiplecourses, with an automatic set-back and shear resistance betweencourses.

[0030] The preferred embodiment will be described in relation to theimpressing of a pre-determined, three-dimensional, rock-like patterninto the front face of a retaining wall block. As a result, the block,and a wall that is constructed from a plurality of the blocks whenstacked into courses, appears to have been constructed with “natural”materials. The process described herein could also be used to constructconcrete blocks that are used in the construction of building walls, aswell as for concrete bricks, slabs and pavers.

[0031] Concrete Block

[0032] A concrete block 10 according to the present invention isillustrated in FIGS. 1-3. The block 10 comprises a block body having afront face 12, a rear face 14, an upper face 16, a lower face 18, andopposed side faces 20, 22. (Note that the terms front, rear, upper, andlower faces reference the orientation of the faces of the block asplaced within a retaining wall and do not necessarily reflect theorientation of the block as it is produced.) The block 10 is formed froma cured, dry cast, no slump concrete. Dry cast, no slump concrete iswell known in the art of retaining wall blocks.

[0033] The front face 12, as shown in FIGS. 1-3, is provided with apre-determined three-dimensional pattern. The pattern on the front face12 is preferably imparted to the front face during molding of the block10 by the action of a moveable stripper shoe (to be later described)having a pattern that is the mirror image of the front face of theblock. FIGS. 14A-C are photos of blocks according to the presentinvention having patterned front faces.

[0034] The pattern that is imparted to the front face 12 can varydepending upon the desired appearance of the front face. Preferably, thepattern simulates natural stone so that the front face 12 appears to bea natural material, rather than a man-made material. The particularstone pattern that is used will be selected based on what is thought tobe visually pleasing to users of the blocks. By way of example, the faceof the block can be impressed with a pattern that appears to be a singlestone, such as river rock. Or the block can be impressed with a patternthat appears to be multiple river rocks in a mortared together pattern.Or the block can be impressed with a pattern that simulates a singlepiece of quarry rubble, or multiple pieces of field stone, stacked inlayers. Endless possibilities are available. By providing stripper shoeswith a variety of different patterns, the resulting patterns on theblocks can be varied by changing stripper shoes.

[0035] The resulting detail and relief that can be provided on the frontface is greater than that which can be provided on a front face of ablock that results from conventional splitting techniques, and thetumbling, hammermilling and other distressing techniques previouslydescribed. The relief on the patterned front face 12, measured from thelowest point to the highest point, is preferably at least 0.5 inches,and more preferably at least 1.0 inches.

[0036] In the preferred embodiment, the front face 12 lies generally inapproximately a single plane between the side faces 20, 22, as opposedto the common, three-faceted and curved faces that are frequently seenin split-face retaining wall blocks, although such multi-faceted andcurved faces can be easily produced with the present invention. As shownin FIG. 3, the front face 12 is provided with a slight rearward slant,i.e. inclined at an angle α from the bottom lower face 18 to the upperface 16. Preferably, α is about 10 degrees. As a result, front and rearfaces 12, 14 are separated by a distance d₁ adjacent the lower face 18and by a distance d₂ adjacent the upper face 16, with d₁ being largerthan d₂. In the preferred embodiment, d₁ is about 7.625 inches and d₂ isabout 6.875 inches. The width d₃ is preferably about 12.0 inches. It isalso contemplated that the front face 12 between the side faces 20, 22can be faceted, curved, or combinations thereof. In these embodiments,the front face would also have a slight rearward slant.

[0037] Typically, when retaining wall blocks are stacked into set-backcourses to form a wall, a portion of the upper face of each block in thelower course is visible between the front face of each block in thelower course and the front face of each block in the adjacent uppercourse. The visible portions of the upper faces create the appearance ofa ledge. And, in the case of dry cast concrete blocks, this ledgetypically has an artificial appearance. By providing a rearward inclineangle to the front face 12 of the block 10, the appearance of the ledgecan be reduced or eliminated, thus enhancing the “natural” appearance ofthe resulting wall.

[0038] The front face 12 also includes radiused edges 24 a, 24 b at itsjunctures with the side faces. The radiused edges 24 a, 24 b are formedby arcuate flanges provided on the stripper shoe. The radius of theedges 24 a, 24 b is preferably about 0.25 inches. The radiused edges 24a, 24 b shift the contact points between the sides of the block 10 withadjacent blocks in the same course, when a plurality of blocks are laidside-by-side, away from the front face 12, and result in better contactbetween the blocks to prevent soil “leakage” between adjacent blocks. Ifdesired, the top and bottom edges at the junctures between the frontface 12 and the upper and lower faces 16, 18 could also be radiused,similar to the radiused edges 24 a, 24 b, by the provision of arcuateflanges on the stripper shoe.

[0039] With reference to FIGS. 1-3, the rear face 14 of the block 10 isillustrated as being generally planar between the side faces 20, 22 andgenerally perpendicular to the upper and lower faces 16, 18. However, itis contemplated that the rear face 14 could deviate from planar, such asby being provided with one or more notches or provided with one or moreconcavities, while still being within the scope of the invention. Thewidth d₄ of the rear face 14 is preferably about 8.202 inches.

[0040] Further, the upper face 16 is illustrated in FIGS. 1-3 as beinggenerally planar, and free of cores intersecting the upper face 16. Whena plurality of blocks 10 is stacked into courses to form a wallstructure, the upper face 16 of each block is in a generally parallelrelationship to the upper faces 16 of the other blocks.

[0041] The lower face 18 of the block 10 is formed so as to be suitablefor engaging the upper face 16 of the block(s) in the course below tomaintain the generally parallel relationship between the upper faces ofthe blocks 10 when the blocks are stacked into courses. In the preferredembodiment, as illustrated in FIGS. 1-3, the lower face 18 is generallyplanar and horizontal so that it is generally parallel to the upper face16. However, other lower faces can be used, including a lower face thatincludes one or more concave portions or one or more channels overportions of the lower face 18. The distance d₆ between the upper face 16and the lower face 18 is preferably about 4.0 inches.

[0042] In the preferred block 10, the side faces 20, 22 are generallyvertical and join the upper and lower faces 16, 18 and join the frontand rear faces 12, 14, as seen in FIGS. 1-3. At least a portion of eachside face 20, 22 converges toward the opposite side face as the sidefaces extend toward the rear face 14. Preferably the entire length ofeach side face 20, 22 converges starting from adjacent the front face18, with the side faces 20, 22 being generally planar between the frontand rear faces 12, 14. However, it is possible that the side faces 20,22 could start converging from a location spaced from the front face 12,in which case the side faces 20, 22 would comprise a combination ofstraight, non-converging sections extending from the front face andconverging sections leading from the straight sections to the rear face14. The converging portion of each side face 20,22 preferably convergesat an angle β of about 14.5 degrees.

[0043] Alternatively, the block 10 can be provided with only oneconverging side face or side face portion, with the other side facebeing substantially perpendicular to the front and rear faces 12, 14. Ablock with at least one converging side face permits serpentineretaining walls to be constructed.

[0044] The block 10 also preferably includes a flange 26 that extendsbelow the lower face 18 of the block, as seen in FIGS. 1-3. The flange26 is designed to abut against the rear face of a block in the coursebelow the block 10 to provide a pre-determined set-back from the coursebelow and provide course-to-course shear strength.

[0045] With reference to FIG. 3A, it is seen that the flange 26 includesa front surface 28 that engages the rear face of the block(s) in thecourse below. The flange 26 also includes a bottom surface 30, a front,bottom edge 32 between the front surface 28 and the bottom surface 30that is arcuate, and a rear surface 34 that is extension of, and forms aportion of, the rear face 14 of the block. The front surface 28 ispreferably angled at an angle γ of about 18 degrees. The angled frontsurface 28 and the arcuate edge 32 result from corresponding shapedportions of the mold, which construction facilitates filling of the moldwith dry cast concrete and release of the flange 26 from the mold.

[0046] As shown in FIGS. 1 and 2, the flange 26 extends the entiredistance between the side faces 20, 22. However, the flange need notextend the entire distance. For example, the flange could extend only aportion of the distance between the side faces, and be spaced from theside faces. Alternatively, two or more flange portions separated fromeach other by a gap could be used.

[0047] With reference to FIG. 3A, the depth d₇ of the flange 26 ispreferably about 0.750 inches. This depth defines the resulting set-backof the block relative to the course below. Other flange dimensions couldbe used, depending upon the amount of desired set-back. The rear surface34 preferably has a height d₈ of about 0.375 inches.

[0048] The concepts described can also be applied to concrete blocksthat are used in the construction of building walls, as well as toconcrete bricks, slabs and pavers. In these cases, it is contemplatedand within the scope of the invention that neither side face of theblock or brick would converge, and that the flange would not be present.However, the patterned front face would provide the block or brick adecorative appearance.

[0049] Block Structures

[0050] The concrete block 10 of the present invention may be used tobuild any number of landscape structures. An example of a structure thatmay be constructed with blocks according to the invention is illustratedin FIG. 4. As illustrated, a retaining wall 40 composed of individualcourses 42 a-c of blocks can be constructed. The blocks used inconstructing the wall 40 can comprise blocks having identicallypatterned front faces, or a mixture of blocks with different, butcompatibly-patterned faces. The height of the wall 40 will depend uponthe number of courses that are used. The construction of retaining wallsis well known in the art. A description of a suitable process forconstructing the wall 40 is disclosed in U.S. Pat. No. 5,827,015.

[0051] As discussed above, the flange 26 on the block 10 providesset-back of the block from the course below. As a result, the course 42b is set-back from the course 42 a, and the course 42 c is set-back fromthe course 42 b. Further, as discussed above, the rearward incline ofthe front face 12 reduces the ledge that is formed between each adjacentcourse, by reducing the amount of the upper face portion of each blockin the lower course that is visible between the front face of each blockin the lower course and the front face of each block in the adjacentupper course.

[0052] The retaining wall 40 illustrated in FIG. 4 is straight. However,the preferred block 10 construction with the angled side faces 20, 22permits the construction of serpentine or curved retaining walls, suchas is disclosed in U.S. Pat. No. 5,827,015.

[0053] Block Forming Process

[0054] An additional aspect of the invention concerns the process forforming the block 10. With reference to FIG. 5, an outline of theprocess is shown. Generally, the process is initiated by mixing the drycast concrete that will form the block 10. Dry cast, no slump concreteis well known in the art of retaining wall blocks. The concrete will bechosen so as to satisfy pre-determined strength, water absorption,density, shrinkage, and related criteria for the block so that the blockwill perform adequately for its intended use. A person having ordinaryskill in the art would be able to readily select a material constituencythat satisfies the desired block criteria. Further, the procedures andequipment for mixing the constituents of the dry cast concrete are wellknown in the art.

[0055] Once the concrete is mixed, it is transported to a hopper, whichholds the concrete near the mold. As discussed below, the mold assembly50 includes at least one block-forming cavity 56 suitable for formingthe preferred block (see FIGS. 6-11). The cavity 56 is open at its topand bottom. When it is desired to form a block, a pallet is positionedbeneath the mold so as to close the bottom of the cavity 56. Theappropriate amount of dry cast concrete from the hopper is then loaded,via one or more feed drawers, into the block-forming cavity through theopen top of the cavity 56. The process and equipment for transportingdry cast concrete and loading a block-forming cavity are well known inthe art.

[0056] The dry cast concrete in the cavity 56 must next be compacted todensify it. This is accomplished primarily through vibration of the drycast concrete, in combination with the application of pressure exertedon the mass of dry cast concrete from above. The vibration can beexerted by vibration of the pallet underlying the mold (tablevibration), or by vibration of the mold box (mold vibration), or by acombination of both actions. The pressure is exerted by a compressionhead, discussed below, that carries one or more stripper shoes thatcontact the mass of dry cast concrete from above. The timing andsequencing of the vibration and compression is variable, and dependsupon the characteristics of the dry cast concrete used and the desiredresults. The selection and application of the appropriate sequencing,timing, and types of vibrational forces, is within the ordinary skill inthe art. Generally, these forces contribute to fully filling the cavity56, so that there are not undesired voids in the finished block, and todensifying the dry cast concrete so that the finished block will havethe desired weight, density, and performance characteristics.

[0057] Pressure is exerted by a stripper shoe 94 that is brought downinto contact with the top of the dry cast concrete in the cavity 56 tocompact the concrete. The stripper shoe 94 acts with the vibration tocompact the concrete within the cavity 56 to form a solid, contiguous,pre-cured block. In the preferred embodiment, the stripper shoe alsoincludes a three-dimensional pattern 96 on its face for producing acorresponding pattern on the resulting pre-cured block as the strippershoe compacts the concrete. Preferably, the portion of the pre-curedblock contacted by the patterned shoe face comprises the front face ofthe block.

[0058] After densification, the pre-cured block is discharged from thecavity. Preferably, discharge occurs by lowering the pallet 82 relativeto the mold assembly, while further lowering the stripper shoe 94through the mold cavity to assist in stripping the pre-cured block fromthe cavity. The stripper shoe is then raised upwardly out of the moldcavity and the mold is ready to repeat this production cycle.

[0059] If the block is to have one or more converging side walls, thencorresponding mold side walls, as described in detail below, must beprovided in the mold. Such mold side walls must be adapted to move intoa first position to permit filling of the mold, and compaction anddensification of the dry cast concrete, and must be adapted to move intoa second position to permit stripping of the mold without damage to thepre-cured block.

[0060] Once the pre-cured block has been completely removed from thecavity, it can be transported away from the mold assembly for subsequentcuring. The block may be cured through any means known to those of skillin the art. Examples of curing processes that are suitable forpracticing the invention include air curing, autoclaving, and steamcuring. Any of these processes for curing the block may be implementedby those of skill in the art.

[0061] Once cured, the blocks can be packaged for storage and subsequentshipment to a jobsite, and can then be used with other cured blocks informing a structure, such as the retaining wall 40 in FIG. 4.

[0062] Mold Assembly

[0063] The mold assembly 50 according to the present invention that isused to practice the invention is illustrated in FIGS. 6-11. The moldassembly 50 is made from materials that are able to withstand thepressure that is applied during formation of the pre-cured block, aswell as provide sufficient wear life.

[0064] The mold assembly 50 is constructed so that the pre-cured blockis formed with its front face facing upward, and with its rear facesupported on the pallet 82 positioned underneath the mold assembly 50.This permits pattern impressing or other direct processing to occur onthe front face 12 of the block, to allow the formation of pre-determinedblock front faces. Pre-determined front faces can include front faceshaving pre-determined patterns and textures, front faces havingpre-determined shapes, front faces made from different material(s) thanthe remainder of the block, and combinations thereof.

[0065] Further, the mold assembly 50 is designed so that a pre-curedblock, including a block with a lower lip or flange and/or one or moreconverging side faces, can be discharged through the bottom of the moldassembly.

[0066] Referring to FIG. 6, the mold assembly 50 comprises a mold 52 anda compression head assembly 54 that interacts with the mold 52 asdescribed below. The mold 52 comprises at least one block-forming cavity56 defined therein. In one preferred embodiment, the mold 52 is sizedfor use in a standard, “three-at-a-time” American block machine, havinga standard pallet size of approximately 18.5 inches by 26.0 inches,which is sized for making three blocks with their upper faces on thepallet. The mold 52 comprises a plurality of generally identicalblock-forming cavities 56. FIG. 7 illustrates five block-formingcavities 56 arranged side-by-side, which is possible when making thepreferred size blocks on a standard “three-at-a-time” pallet. Of course,larger machines that use larger pallets are in use, and this technologycan be used in both larger and smaller machines. The number of possiblemold cavities in a single mold depends upon size and/or type of themachine and the size of the pallet. A plurality of block-formingcavities 56 allows increased production of blocks from the single mold52.

[0067] With reference to FIG. 7, the cavities 56 are formed by divisionplates 58, including a pair of outside division plates, a plurality ofinside division plates, and a pair of end liners 60 that are common toeach cavity 56. The use of outside and inside division plates and endliners to form a block-forming cavity in a mold is known to those ofskill in the art. The division plates and end liners form the boundariesof the block cavities and provide the surfaces that are in contact withthe pre-cured blocks during block formation, and are thus susceptible towear. Thus, the division plates and end liners are typically mounted forremoval within the mold 52 so that they can be replaced as they wear orif they become damaged. The techniques for mounting division plates andend liners in a mold to form block cavities, and to permit removal ofthe division plates and end liners, are known to those of skill in theart.

[0068] In the preferred embodiment, the division plates 58 form theupper and lower faces 16, 18 of the blocks 10, while the end liners 60form the side faces 20, 22. For convenience, the division plates and endliners will hereinafter (including in the claims) be referred tocollectively as the side walls of the cavities. Thus, side walls refersto division plates and end liners, as well as to any other similarstructure that is used to define the boundaries of a block-formingcavity.

[0069] Referring now to FIG. 8, a portion of a single block-formingcavity 56 is illustrated. The cavity 56 defined by the side walls 58, 60has an open top 64 and an open bottom 66. As shown, the top ends of theside walls 60 (e.g. the end liners) are connected by pivots 62 tosuitable surrounding structure of the mold 52 to allow the side walls 60to pivot between the closed position shown in FIG. 8, where the sidewalls 60 converge toward each other, to a retracted position where theside walls 60 are generally vertical and parallel to each other (notshown). In the retracted position, the bottom of the cavity 66 is atleast as wide as the top of the mold cavity, which allows the pre-curedblock to be discharged through the open bottom. When only a portion ofeither side face 20, 22 of the block converges, only a correspondingportion of the side walls 60 will be pivoted. The side wall 58 thatforms the lower face of the block 10 is also illustrated in FIG. 8,while the other side wall 58 that forms the upper face of the block isnot shown.

[0070] Pivoting of the side walls 60 is required in order to form thepreferred block 10. As discussed above, the block 10 is formed “face-up”in the mold 52 with its converging side faces formed by the side walls60. Thus, the converging side walls 60, when they are angled asillustrated in FIG. 8, shape the converging side faces 20, 22 of thepre-cured block. However, the front portion of the pre-cured block iswider than the rear portion of the block. In order to be able todischarge the pre-cured block through the open bottom 66, the side walls60 must pivot outward to enable downward movement of the pre-cured blockthrough the open bottom.

[0071] Biasing mechanisms 68 are provided to maintain the side walls 60at the converging position during introduction of the concrete andsubsequent compacting of the dry cast concrete, and which allow the sidewalls 60 to pivot to a vertical position during discharge of thepre-cured block. Preferably, a single biasing mechanism 68 is connectedto each side wall 60 that is common to all cavities 56, so that themovement of each side wall 60 is controlled via a common mechanism (seeFIG. 7). Alternatively, separate biasing mechanisms can be provided foreach cavity. The biasing mechanisms 68 are illustrated as comprising airbags, which will be controlled through the use of air or similar gas.Suitable inlet and outlet ports for the air will be provided, as will asource of high pressure air. The use of biasing mechanisms other thanair bags is also possible. For example, hydraulic or pneumatic cylinderscould be used.

[0072] When pressurized with air, the air bags will force the side walls60 to the position shown in FIG. 8. When it comes time to discharge thepre-cured block(s), the pressurized air is vented from the air bags,which allows the side walls 60 to pivot outward under force of thepre-cured block as the pre-cured block is discharged through the openbottom when the pallet is lowered. During block discharge, the sidewalls 60 remain in contact with the side faces of the pre-cured block.Alternatively, biasing mechanisms, such as coil springs, can beconnected to the side walls 60 to force the side walls to the retractedposition when the air bags are vented. In this case, as the pallet 82starts to lower to begin block discharging, the side walls 60 will beforced to the retracted position, and the side walls 60 will not contactthe side faces of the block during discharge. After discharge, the sidewalls 60 are returned to the closed, angled position by re-pressurizingthe air bags.

[0073] Rather than pivoting the side walls 60, it is possible to useother mechanisms to permit movement of the side walls 60 to allowdischarge of the pre-cured block. For example, the side walls 60 couldbe mounted so as to slide inwards to the position shown in FIG. 8 andoutwards to a position where the bottom of the cavity 56 is at least aswide as the top of the mold cavity. The sliding movements could beimplemented using a track system in which the side walls are mounted.

[0074] As shown in FIG. 8, each side wall 60 includes a shaping surface76 that faces the cavity 56. The shaping surfaces 76 are substantiallyplanar. The result is the formation of substantially planar side faces20, 22 of the block 10.

[0075] Referring now to FIG. 9, the side walls 58 that form the upperand lower faces 16, 18 of the block 10 are illustrated. The side walls58, which are fixed and not moveable during the molding process, aresubstantially vertical.

[0076] The side wall 58 that forms the upper face 16 (the left side wall58 in FIG. 9) includes a shaping surface 78 that faces the cavity 56.The surface 78 is substantially planar, which results in the formationof a substantially planar upper face 16.

[0077] The side wall 58 that forms the lower face 18 (the right sidewall 58 in FIG. 9) includes an undercut, or “instep,” portion 80 at thebottom edge thereof adjacent the open bottom 66. The undercut portion80, in combination with the pallet 82 that is introduced under the mold52 to temporarily close the open mold bottom 66 during the moldingprocess, defines a flange-forming subcavity of the cavity 56. Theflange-forming subcavity has a shape that results in the formation ofthe flange 26 on the block 10.

[0078] In particular, the undercut portion 80 includes a shaping surface84 that forms the front surface 28 of the flange 26, a shaping surface86 that forms the bottom surface 30 of the flange, and a shaping surface88 that forms the edge 32 of the flange 26. The portion of the flange 26that is an extension of the rear face 14 is formed by and on the pallet82, along with the remainder of the rear face 14. The shape of thesurfaces 84 and 86 facilitate filling of the undercut portion 80 withthe concrete during introduction and subsequent compacting of theconcrete so that the flange 26 is completely formed, as well as aid inrelease of the flange 26 from the surfaces 84, 86 during blockdischarge.

[0079] In the case of a block having a flange on the lower face and noconverging side faces, the side walls 60 would be oriented verticallyinstead of being converging. Further, in the case of a block without aflange on the lower face and with converging side faces, the undercut 80would not be present. In the case of a block without a flange on thelower face and without converging side faces, the undercut 80 would notbe present and the side walls 60 would be oriented vertically.

[0080] Returning to FIGS. 6 and 8, the head assembly 54 is seen toinclude a compression head 90 in the form of a plate. The head 90 isactuated by an actuating mechanism in a manner known in the art so thatthe head 90 is moveable vertically up and down to bring about compactionof the dry cast concrete in the mold cavities 56 and to assist instripping the pre-cured blocks from the mold 52.

[0081] Connected to and extending from the bottom of the head 90 is aplurality of stand-offs 92, one stand-off for each block-forming cavity56 as shown in FIG. 6. The stand-offs 92 are spaced from each other,with the longitudinal axis of each stand-off oriented perpendicular tothe plane of the head 90 and extending generally centrally through theblock-forming cavity 56.

[0082] Stripper Shoe

[0083] A stripper shoe 94, illustrated in FIGS. 6, 8, 9 and 11, isconnected to the end of each stand-off 92. The stripper shoe 94 isrectangular in shape and is dimensioned so that it may enter therespective cavity 56 through the open top to contact the concrete tocompact the concrete, and to travel through the cavity during dischargeof the pre-cured block. The dimensions of the stripper shoe 94 are onlyslightly less than the dimensions of the open top 64 of the cavity 56,so that the shoe 94 fits into the cavity 56 with little or no spacingbetween the sides of the shoe 94 and the side walls 58, 60 defining thecavity. This minimizes escape of concrete between the sides of the shoe94 and the side walls 58, 60 during compression, and maximizes the frontface area of the block that is contacted by the shoe 94.

[0084] Flanges 98 a, 98 b are formed on opposite ends of the face of thestripper shoe 94, as best seen in FIG. 11. The flanges 98 a, 98 b arearcuate to produce the rounded edges 24 a, 24 b on front face 12 of theblock. If desired, arcuate flanges can be provided on the two remainingends of the stripper shoe 94, in order to produce upper and lowerrounded edges on the front face 12.

[0085] As discussed above, a face of the shoe 94 is preferably providedwith a pre-determined pattern 96 that is a reverse image of a desiredsurface or surfaces. As the shoe 94 including the pattern 96 compactsthe concrete, the pattern is imparted to the front face of the block.The pattern 96 preferably simulates natural stone, so that the frontface of the resulting block simulates natural stone thereby making theblock appear more natural and “rock-like.” A variety of differentpatterns 96 can be provided on the shoe 94, depending upon theappearance of the front face that one wishes to achieve. In addition to,or separate from, the pattern 96, the face of the shoe 94 can be shapedto achieve a faceted or curved block front face. Indeed, the face of theshoe 94 can be patterned and/or shaped in any manner which one desiresin order to achieve a desired appearance of the block front face.

[0086] FIGS. 10A-F and 11 provide examples of patterns 96 that can beprovided on the shoe 94. The patterns 96 simulate naturally occurringobjects, such as, for example, natural stone or man made objects. Thepattern 96 is preferably machined into the shoe face based upon apre-determined three-dimensional pattern. An exemplary process forcreating the pre-determined pattern 96 on the shoe face follows.

[0087] Referring now generally to FIG. 12, initially, one or moreobjects are selected. For example, the objects may include one or morenatural rocks having surfaces which one considers to be visuallypleasing. Other natural or man made objects may also be used.

[0088] One or more of the rock surfaces are then scanned using a digitalscanning machine. An example of a suitable scanning machine forpracticing the invention is the Laser Design Surveyor® 1200 having anRPS 150 head, available from Laser Design Incorporated of Minneapolis,Minn. The Laser Design Surveyor® 1200 has a linear accuracy of 0.0005inch in the XYZ coordinates, and a resolution of 0.0001 inch. Aspracticed, data is collected at 256 points for every 0.004 inch of theone or more rock surfaces being scanned. The rock surfaces may bescanned at as many angles as necessary to collect data on all surfaces.

[0089] Once the scanned data has been collected, various techniques canbe used to manipulate the data. Initially, the Laser Design Surveyor®utilizes DataSculpt® software, available from Laser Design, Inc. ofMinneapolis, Minn., to generate one or more DataSculpt® point clouds, ordata sets including data points positioned in X, Y, and Z coordinates,from the scanned data.

[0090] A computer-aided design (CAD) package is then used to trim thepoint clouds. The point clouds are also sampled to reduce the scanneddata to a manageable size, while smoothing the data by removingextraneous points and noise. Next, the data from the point clouds areblended to form a finished point cloud. The finished point cloud isconverted to a polygonal mesh, or a three-dimensional rendition of thepoint cloud using polygonal shapes. The edges of the polygonal mesh aretrimmed to form a clean line, and boundaries are applied to form a tightmesh pattern. Using the mesh, grids are applied and converted to aNon-Uniform Rational B-Splines (NURBS) surface.

[0091] The resulting digital image is displayed (see, e.g., FIGS.10A-F). The user can manipulate the digital image by selecting andmodifying one or more points on the digital image in the X, Y, and/or Zdirections. Next, the data is scaled and/or trimmed to an overall blockdimension, in the illustrated embodiment 3.88 inches by 11.88 inches perprint. In addition, the data is modified to meet a ¾ inch maximumdifference in face relief, a 0-10 degree face angle from the lower edgeof the face to the upper edge of the face, and a 5-10 degree draft forall interior surfaces of the relief. Next, the complete data file ismirrored to create the reverse image needed to create the stripper shoe94. The data can be output in an Initial Graphics Exchange Specification(IGES) format to a CAD system described below.

[0092] A CAD system suitable for manipulating the scanned data is theMastercam® Mill Version 8.1.1, available from CNC Software, Inc. ofTolland, Conn.

[0093] The data, in IGES format, is then input into preferably a threeaxis (or four axis), numerically controlled milling machine for millingof the stripper shoe 94. The data is converted into toolpaths by themilling machine. Using the toolpaths, the milling machine mills a mirrorimage of the rock surface into the face of the stripper shoe 94.

[0094] To create the illustrated stripper shoes, the milling machine canperform a series of toolpaths, including: (1) a first toolpath with a ½inch diameter flat bottom endmill doing a parallel pocket at 90 inchesper minute (IPM) and 7,000 revolutions per minute (RPM); (2) a secondtoolpath with a ¼ inch diameter flat bottom endmill doing a surfacecontour at 100 IPM and 10,000 RPM; (3) a third toolpath with a ¼ inchdiameter ball endmill doing a 45° surface contour at 100 IPM and 12,000RPM; and (4) a fourth toolpath with a ⅛ inch diameter ball endmill doinga 45° surface contour at 150 IPM and 14,000 RPM. The number and type oftoolpaths may vary based on the complexity of the surface beingreproduced.

[0095] A suitable milling machine for practicing the invention is theMikron VCP600 available from Mikron AG Nidau of Nidau, Switzerland.

[0096] The result is a pattern milled into the face of the shoe 94 thatis a mirror image of the desired pattern of a block. When the shoe 94including the pattern compacts the concrete used to form the block, thepattern is impressed into the front face of the block. In theillustrated embodiments shown in FIGS. 10A-F and 11, the resultingthree-dimensional pattern has a relief of between about 0.5 inch andabout 1.0 inch, preferably no greater than about ¾ inch.

[0097] This process can be repeated to produce additional shoes havingthe same or different face patterns. This is advantageous because thepatterned face of each shoe is subject to wear, and the shoe will needto be replaced when the pattern becomes excessively worn. Moreover,multiple shoes can be used for multiple molds. Further, by forming avariety of different pre-determined shoe patterns, a variety ofdifferent block front face appearances can be achieved. Other shoepatterns can be formed by combining the scanned surfaces of a pluralityof different rocks. Exemplary shoe patterns are illustrated in FIGS.10A-F and 11.

[0098] As discussed above, the resulting detail and relief that isprovided on the block front face can be significantly greater than thedetail and relief that is provided on the front face of a block thatresults from conventional splitting techniques, and the other front facedistressing techniques discussed above. If desired, the scan data can bemanipulated in order to increase or decrease the relief that is milledinto the shoe face, which will alter the relief that is ultimatelyprovided on the block front face.

[0099] It is known in the art that dry cast concrete may have a tendencyto stick to mold surfaces, such as the patterned surface of the strippershoe 94. Various techniques to enhance the release of the stripper shoe94 from the dry cast concrete are known, and one or more of them mayneed to be employed in the practice of this invention. For example, thepattern formed on the stripper shoe has to be designed to enhance,rather than inhibit, release. In this regard, appropriate draft angleshave to be employed in the pattern. As noted above, in the illustratedembodiment, a draft angle of 5° is used. The pattern-forming techniquesdescribed above permit manipulation of the scanned images to createappropriate draft angles. Release agents, such as a fine mist of oil,can be sprayed onto the stripper shoe between machine cycles. Headvibration can be employed to enhance release. And heat can be applied tothe stripper shoe to enhance release. Heating mold components to preventsticking of dry cast concrete is known in the art. In the presentinvention, due to the detailed pattern that is to be imparted to theblock front face, it is even more important to prevent sticking. Inparticular, it is important to be able to control the temperature of theshoe so that the temperature can be maintained at selected levels.

[0100] Preferably, as shown diagrammatically in FIG. 13, a heater 100 isconnected to the shoe 94 for heating the shoe. The heater 100 iscontrolled by a temperature control unit 102. A thermocouple 104 mountedon the shoe 94 senses the temperature of the shoe, and relays thatinformation to a power control unit 106 that provides electrical powerto the control unit 102 and the heater 100. The system is designed suchthat, when the temperature of the shoe 94 falls below a pre-determinedlevel as sensed by the thermocouple 104, power is provided to the heater100 to increase the shoe temperature. When the shoe temperature reachesa pre-determined level, as sensed by the thermocouple, the heater 100 isshut off. Thus, the shoe temperature can be maintained at selectedlevels. Preferably, the control unit 102 is designed to allow selectionof the minimum and maximum temperature levels, based on the dry castconcrete that is being used. In the preferred embodiment, the surfacetemperature of the stripper shoe 94 is maintained between 120° F. and130° F.

[0101] The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

What is claimed is:
 1. A method of making a stripper shoe for impressinga three-dimensional pattern into no slump concrete that has beendeposited into a concrete unit mold to form an uncured concrete unithaving a face with the three-dimensional pattern, comprising: selectinga desired three-dimensional surface from at least one existing naturallyoccurring or man made object; digitally scanning the selectedthree-dimensional surface to create scanned data; and using the scanneddata to machine a face of the stripper shoe with a three-dimensionalpattern that is a mirror image of the selected three-dimensionalsurface.
 2. The method of claim 1, including the step of displaying thescanned data prior to the step of using the scanned data to machine aface of the stripper shoe.
 3. The method of claim 2, includingmanipulating the displayed scanned data to modify the three-dimensionalpattern, and using the manipulated scanned data to machine the face ofthe stripper shoe.
 4. The method of claim 1, including machining thethree-dimensional pattern into the face of the stripper shoe so that ithas a maximum relief of at least about 0.5 inches.
 5. The method ofclaim 4, wherein the maximum relief is at least about 1.0 inch.
 6. Themethod of claim 1, comprising selecting the desired three-dimensionalsurface from at least one stone.
 7. The method of claim 6, comprisingselecting the desired three-dimensional surface from a plurality ofstones.
 8. The method of claim 6, comprising digitally scanning at leastone surface of the stone.
 9. The method of claim 1, comprising forming aflange along at least a portion of the perimeter of the stripper shoeface.
 10. A stripper shoe for stripping an uncured concrete unit from acavity of a concrete unit mold, the concrete unit being molded from noslump concrete that is deposited into the cavity of the concrete unitmold, comprising: a metal plate having opposite major surfaces, and aperimeter edge, wherein the perimeter edge of the metal plate is sizedto fit into the cavity of the mold to enable the metal plate to travelthrough the mold cavity as the concrete unit is stripped from the mold;and a three-dimensional pattern formed in one of the major surfaces ofthe metal plate, the three-dimensional pattern being a mirror image of apre-existing three-dimensional surface from one or more naturallyoccurring or man made objects.
 11. The stripper shoe of claim 10,wherein the three-dimensional pattern on the major surface of the platehas a relief of at least about 0.5 inches.
 12. The stripper shoe ofclaim 11, wherein the relief is at least about 1.0 inch.
 13. Thestripper shoe of claim 10, wherein the three-dimensional pattern isgenerated by digitally scanning the one or more naturally occurring orman made objects.
 14. The stripper shoe of claim 10, further comprisinga flange along at least a portion of the major surface of the strippershoe containing the three-dimensional pattern.
 15. A method of making aconcrete unit with a face having a three-dimensional pattern,comprising: selecting a desired three-dimensional surface from at leastone existing naturally occurring or man made object; digitally scanningthe selected three-dimensional surface to create scanned data; using thescanned data to machine a face of a stripper shoe with athree-dimensional pattern that is a mirror image of the selectedthree-dimensional surface; depositing no slump concrete into a concreteunit mold; pressing the three-dimensional patterned face of the strippershoe into the no slump concrete in the concrete unit mold to reproducethe mirror image of the stripper shoe face in the no slump concrete inthe concrete unit mold; stripping the concrete unit from the concreteunit mold; and curing the concrete unit.
 16. The method of claim 15,including the step of displaying the scanned data prior to the step ofusing the scanned data to machine a face of the stripper shoe.
 17. Themethod of claim 16, including manipulating the displayed scanned data,and using the manipulated scanned data to machine the face of thestripper shoe.
 18. The method of claim 15, including machining thethree-dimensional pattern into the face of the stripper shoe so that ithas a relief of at least about 0.5 inches.
 19. The method of claim 18,wherein the relief is at least about 1.0 inch.
 20. The method of claim15, comprising selecting the desired three-dimensional surface from atleast one stone.
 21. The method of claim 20, comprising selecting thedesired three-dimensional surface from a plurality of stones.
 22. Themethod of claim 20, comprising digitally scanning at least one surfaceof the stone.
 23. The method of claim 15, comprising forming a flangealong at least a portion of the perimeter of the stripper shoe face.